The present invention relates generally to the field of orientation sensors and, more particularly, to an orientation sensor including a conductive pattern including isolated conductive segments configured for segment to segment (hereinafter intra-pattern) property measurements useful in establishing one or more orientation parameters. The sensor is suitable for use in applications such as, for example, monitoring a remotely controlled underground boring device.
A number of orientation sensors have been designed especially for use in remote controlled underground boring devices. As will be seen, these prior art devices have shared a basic design concept.
One example of a prior art orientation sensor in the form of a roll sensor is disclosed in U.S. Pat. No. 5,174,033 (Rider). FIGS. 1 and 2 are partial reproductions of FIGS. 4 and 5, respectively, of the Rider patent. FIG. 1 shows a roll sensor generally indicated by the reference number 10. Sensor 10 includes a substrate 12 and a cup-shaped member 14 which is sealed to substrate 12 by an O-ring 16 in a way which defines a cavity 18. A conductive fluid 20 is contained by cavity 18.
Attention is now directed to FIG. 2 in conjunction with FIG. 1. FIG. 2 illustrates a plurality of capacitor electrode plates 22 which are formed on the inner surface of substrate 12. Electrical connections to capacitor electrode plates 22 are accomplished via a plurality of electrically conductive leads 24. Cup-shaped member 14 serves as a grounded electrode common to all of electrode plates 22. During operation, roll sensor 10 is designed to spin in the plane of FIG. 2, oriented such that gravity causes fluid 20 to continuously flow into the bottom portion of the cavity (FIG. 1). The roll orientation of sensor 10 is determined by measuring the capacitance between individual electrode plates 22 and cup-shaped member 14 as influenced by fluid 20. It is important to note that measurements are taken, in essence, between the ends of the device. Moreover, it is submitted that prior art orientation sensors, in general, operate under the concept of using measurements taken along the length of the device. That is, by using electrically conductive members positioned at least at the ends of the device and/or centered therebetween or at other intermediate locations. For other examples, see U.S. Pat. Nos. 4,674,579, 4,714,118 and 5,726,359. As will be seen, the present invention eliminates the need for an implementation having electrodes at both ends of a device or spaced apart therebetween, introducing a highly advantageous and heretofore unseen configuration useful in measuring pitch and/or roll.
As will be described in more detail hereinafter, there is disclosed herein an orientation sensor capable of generating at least one output signal indicative of a particular orientation parameter. The orientation sensor comprises a sensor housing defining a closed internal chamber including a first internal surface. The first internal surface supports a first electrically conductive pattern which itself forms part of a sensing arrangement. The first electrically conductive pattern includes an arrangement of electrically isolated segments in a predetermined configuration. A flowable material is contained within the internal chamber, which flowable material contacts a portion of the first internal surface dependent upon the value of the particular orientation parameter.
In one aspect of the invention, an electrical property is measurable between the segments such that the orientation parameter can be determined using the output signal based only on the electrical property and, therefore, only on the portion of the first internal surface contacted by the flowable material. Thus, intra-pattern measurements yield the measured property without the need for conductive members distributed along the length of the chamber.
In another aspect of the invention, the particular orientation parameter is pitch. In this instance, a first electrically conductive pattern includes first and second electrically isolated segments defining a gap therebetween on the first internal surface such that the value of the electrical property is in proportion to an area of the gap covered by the flowable material between the first and second segments which, in turn, is in proportion to the pitch so as to cause the value of the electrical property between the first and second segments to change in response to changes in pitch.
In still another aspect of the invention, the particular orientation parameter is roll angle. In this instance, the first electrically conductive pattern includes at least first and second electrically isolated segments defining a first roll sensing gap therebetween on the first internal surface such that the value of the electrical property is in proportion to an area of the roll sensing gap covered by the flowable material between the first and second segments which, in turn, is in proportion to the roll so as to cause the value of the electrical property between the first and second segments to change in response to changes in roll. In one feature, the electrically conductive pattern defines a plurality of roll sensing gaps, each of which covers a particular range of roll positions of the orientation sensor. In one preferred embodiment, the electrically conductive pattern defines three roll sensing gaps that are configured so as to substantially surround a common center point about which the orientation sensor experiences roll. Each roll sensing gap is used to produce an output such that the roll position of the orientation sensor is unambiguously identifiable either statically or dynamically.
In yet another aspect of the present invention, an orientation sensor is provided which is capable of generating at least two output signals indicative of a particular orientation parameter. The orientation sensor comprises a sensor housing defining a closed internal chamber having first and second opposing internal surfaces. A first electrically conductive pattern is supported by the first internal surface and a second electrically conductive pattern is supported by the second internal surface. The first electrically conductive pattern includes a first plurality of electrically isolated segments in a first predetermined configuration while the second electrically conductive pattern includes a second plurality of electrically isolated segments in a second predetermined configuration. A flowable material is contained within the internal chamber such that the flowable material contacts first and second portions, respectively, of the first and second internal surfaces. The respective areas of the first and second portions contacted by the flowable material are dependent upon the value of the particular orientation parameter in a way which influences an electrical property measurable between the segments disposed on the first and second surfaces such that the first electrically conductive pattern produces at least a first output signal and the second electrically conductive pattern produces at least a second output signal. In one feature of the present invention, each pattern produces its output signal substantially independent of the other pattern based on contact with the flowable material.
In another feature of the present invention, the first and second electrically conductive patterns are identical and identically oriented such that combined use of the output signals to determine the value of the orientation parameter produces ratiometric cancellation of temperature error.
In one implementation according to the present invention, a combination pitch and roll orientation sensor is provided having a housing containing a flowable material which flows in the housing in response to the pitch and roll orientation of the housing. An electrical arrangement includes a single electrically conductive pattern cooperating with the flowable material so as to produce independent electrical signals corresponding to the pitch and roll of the housing.